1. Field of the Invention
The invention relates generally to automatic titration devices and, more particularly, but not by way of limitation, it relates to an improved titration apparatus that can be used on-line with continuous selected liquids processing or in a batch processing mode.
2. Description of the Prior Art
The prior ar includes various types of titration device. At present, titration is generally performed by placing a solution in a container while another known chemical is slowly introduced to the solution. An operator can then monitor the mixing process to attempt to detect a color change in the mixture, such color change being indicative of an equivalence point in the mixture. The color change detection may be done visually or by a commercial type of color detector. U.S. Pat. No. 2,977,199 discloses a continuous testing device that may be employed with flowing liquids. In this device, a small portion of the flowing liquid is tapped off for introduction to a mixing chamber and subsequent flush to disposal. A controlled volume of titrant is introduced from a storage tank into the mixing chamber and a sensing device with indicator electrode, e.g. a platinum-rhenium alloy electrode, senses a potential change to provide an indication of the end point of the sample solution. The patent also discloses a situation where a colorimetric pH indicator is employed after mixing to provide a means for identifying the solution end-point.
U.S. Pat. No. 4,920,056 provides another teaching of an automated system for liquid-phase analysis. In this apparatus, a specified liquid sample and up to five reagents are delivered to a reaction cell by a stepper motor-driven syringe, and the contents of the cell are then mixed by spinning the cell. Sensing of the contents of the cell is done by a pH probe that derives an end point indication. The subject of the patent is to perform batch-mode liquid-phase reactions for chemical analysis on a microscale. The apparatus includes a reactor for receiving liquid from an automatic liquid sample injection valve and an automatic liquid reagent valve. A programmable electronic timer is then used to automatically control the injection and reagent valves in a programmed sequence and the analysis is completed by introducing the reaction mixture to a flow-through photometric detector to determine a reaction product of the sample and the reagent. Various types of sensor may be used to examine the reactor output.
Finally, another automatic titrator of the photometric type is taught in U.S. Pat. No. 3,073,682 wherein samples are delivered and tested in batch form. The device includes a titrating cell and means to feed a measured sample of main solution plus titrant thereto. Thereafter, a control circuit determines the end point of titration as well as a measure or indication of the volume of titrant added to effect neutralization of the particular sample. This device has desirable attributes of cleanliness and preservation of the purity of sample materials.